Method and means for reproducing balanced sound records



Oct. 11, 1938. G. CLAMANN 2,133,132

METHOD AND MEANS FOR REPRODUCING BALANCED SOUND RECORDS Filed Nov. 4,1937 2 Sheets-Sheet l OUTPUT DBJCUR/NG WEDGE 4 69 OUTPUT L Q Ger/lardClam (27m Oct. 11, 1938. Q G.'CLAMANN 2,133,132

METHOD AND MEANS FOR REPRODUCING BALANCED SOUND RECORDS Filed Nov. 4,1957 2 Sheets-Sheet 2 awn/r oum/r v jizderdvf Ger/M722 C lamalm PatentedOct. 11, 1938 UNITED STATES METHOD AND MEAN BALANCED SO Gerhard Clamann,Dresden,

S FOR REPRODUOING UND RECORD-S Germany, assignor to Zeiss IkonAktiengesellschaft, Dresden, Germany Application November 4 1937, SerialNo. 172,744

In Germany November 19, 1936 7 Claims.

The invention relates method and means for sound records.

Sound records of this type are produced by recording the positive waveportions and the negative wave portions of the oscillation to berecorded upon separate sound tracks. In the reproduction of theserecords, the sound tracks are separatelyscanned. Afterhavingbeenscannedseparately, the two half-wave portions are combined to form the originaloscillation. Since the two half-wave portions are locally spaced on therecord carrier, which for instance may consist of a film, but in otherrespects are completely equivalent, it is necessary when recombining thehalf-Wave portions for the purpose of reproduction to invert the phaseof one of these halfwave portions.

It has been proposed heretofore to employ for the purpose stated twophotoelectric tubes which either are connected in opposition to eachother or are connected by means of a coupling transformer, which efiectsthe inversion of the phase, with the first amplifier tube. It is alsoknown to employ a single balancing tube provided with a single cathodeand two separated anodes in an appropriate circuit arrangement.

All of these prior arrangements have the disadvantage that they requirea considerable number of auxiliary elements, as for instance,resistances, condensers and transformers. Certain of these elements haveto be arranged at the input of the amplifier and are extremely sensitiveto electrical or magnetical disturbances. As an example of such anelement maybe mentioned the coupling transformer between thephotoelectric tube and the grid of the first amplifier tube. On theother hand, certain of these auxiliary elements have to be located inmost instances directly at the sound scanning station where owing tolack of space, these elements can be arranged with difficulty only.

It is now the principal object of the invention to eliminate thedisadvantages inherent in the arrangements of the prior art. Accordingto the invention one of the two sound tracks representing one-half waveof the oscillation is scanned by a photo-electric tube from which theelectrons enter the outer circuit in one direction while the other soundtrack, representing the other half-wave of the oscillation, is scannedby another photo-electric tube through which the electrons pass in theopposite direction.

One object of the invention therefore is to use for the scanning of thetwo sound tracks to improvements in a reproducing balanced twoseparately arranged and different light sensitive elements and anotherobject of the invention is to employ for the same purpose a single lightsensitive element provided with a common cathode and two spaced anodes.

In the drawings: a

Fig. 1 illustrates diagrammatically an arrangement employing twoseparate photo-electric tubes, and d Fig. 2 illustrates diagrammaticallya modified arrangement employing a single photo-electric tube providedwith a common cathode and two anodes, and Figs. 3, 4 and 5 illustratemodifications of the arrangement of Fig. 2.

In Fig. 1 the photo-electric tube I is of conventional construction,while therphoto-electric tube 2 is constructed to effect a release ofsecondary electrons thereby causing the desired inversion of the phase.Theanodes 3 and 4 of the tubes l and 2 respectively are connected witheach other by a conductor 5. The photoelectric tube 2 is equipped withan auxiliary anode 6 of screen formation. This auxiliary anode 6 is.arranged to surround the primary anode 4 of the tube 2. The auxiliaryanode 6 isrelated to the cathode 1 in a manner to permit passage ofalternating current only and also has with respectto the cathode 1 apositive potential. This positive potential ishigher than the negativepotential applied to the main anodes 3 and 4. The condenser 8 and thecoupling resistors 9 and ID are of conventional construction and areused for connecting the photo-electric tubes to the input tube ll of theamplifier. These conventional elements may be conveniently mountedwithin the amplifier structure.

Fig. 2 illustrates a modified embodiment in which the anodes andcathodes of the two separate photo-electric tubes of Fig. 1 are locatedwithin the same envelope l2. The two anodes, however, are combined toform the common cathode l3. In this figure, the anodes are indicated at14 and I 5, and the anode I5 is sur rounded by an auxiliary screen anodel6. common cathode I3 is provided with a shield '28 for preventing thefiow of electrons from one cathode portion to the other.

The auxiliary screen anode I6 is related to the cathode l3 to permitpassage of alternating current only and again has a positive potentialwith respect to the cathode. This positive potential supplied by adirect current source 15 higher than the negative voltage applied tothetwo anodes l4 and I5. The condenser l1 and the coupling resistors l8 andI9 are again of con- The I ventional construction and are used forconnecting the photoelectric tube with the input tube 2| of theamplifier. These conventional connector elements may be convenientlymounted within the amplifier structure.

The operation of these two arrangements is the same. It is described inthe following with reference to the second embodiment.

A beam of light scanning one of the two sound tracks (not shown) may beassumed to strike the cathode l3 solely on one side of the cathode. Theother beam of light, scanning the other sound track, strikes the cathodesolely on the other side of the shield 20, namely the right hand portionof the cathode in such manner, that in accordance with the principle ofbalanced scanning one portion of the cathode is dark, while the otherone is illuminated, and vice versa. The light impulses acting upon theleft hand portion of the cathode l3 release in known manner aphoto-current which causes a corresponding drop of voltage in theresistors I8 and IS. The light impulses striking the portion of thecathode on'the right side of the shield 20 produce primarily aphotocurrent of the same value and direction as produced by the otherhalf of the tube. But when the electrons strike the anode l5, which isconstructed so as to emit secondary electrons, a current of secondaryelectrons is released, which secondary electrons are attracted by theauxiliary anode l6 provided the latter is positively charged withrespect to the anode [5. A flow of electrons from the anode l5 to theauxiliary anode l6 therefore takes place. The outer current resultingfrom this condition consists of the difference between the flow ofelectrons'striking the anode and the fiow of electrons leaving theanode.

If now, the ratio:

number of secondary electrons 2 number of primary electrons then theouter current upon illumination of the right hand portion of the cathodel3 has the same intensity, but is of opposite phase as the currentproduced upon illumination of the left hand portion of the cathode l3; 7

The anode l5 as already stated above, consists of a material having thecapacity of emitting a strong flow of secondary electrons.

The ratio value 2 referred to above need not be adhered to veryaccurately. The same balancing condition may be attained by varying thevoltage difference between the auxiliary anode l6 and the main anodes l4and I5, or it may be attained by providing the anode H! with a-separatepotential. This separate potential may then be adjusted in such mannerthat sensitiveness of the anode I4 is made equal to the sensitiveness ofthe anode l5 emitting secondary electrons, which applies particularly togas filled tubes.

Finally, the balancing of sensitiveness may also be attained byarranging in one or both branches of the path of light to thephotoelectric tube or tubes diaphragms, obscuring wedges or similarelements. 7

What I claim is: v I

1. In a method of reproducing balanced double track sound records, thesteps of separately scanning photoelectrically the half waves in eachtrack of the sound record and producing a multiple of secondaryelectrons by the primary electrons generated during the scanning of oneof said sound tracks, so that the electron flow resulting from thetwoemissions of electrons flows in a direction opposite to the flow ofthe primary electrons produced during the scanning or the other one ofsaid sound tracks, whereby the two half-waves of the sound recordreproduced thereby are arranged in phase opposition.

2. In a system for reproducing balanced double track sound records, thecombination of two light sensitive elements, one for each sound trackand adapted to be energized by a beam of light scanning the half-wavesin the sound track, one of said elements being provided with means forcausing the electrons generated by the light scanning the sound track toproduce multiplied secondary electrons so that the resulting electroncurrent in said light sensitive element flows in a direction opposite tothe flow of the electrons produced in the other light sensitive element,whereby the two half-waves of the sound record reproduced thereby arearranged in phase opposition.

3. In a system for reproducing balanced double track sound records, thecombination of two photoelectric tubes, one for each sound track andadapted to be energized by a beam of light scanning the half-waves insaid soundtrack, one of said photoelectric tubes being provided with ananode adapted to emit multiplied secondary electrons when struck by theprimary electrons produced in response to the beam of light scanning thesound track, an auxiliary anode associated with said anode forattracting said secondary electrons and effective to invert the phase ofthe half-waves of the respective sound track, whereby the two half-wavesof the sound record reproduced thereby are arranged in phase opposition.s

4. In a system for reproducing balanced double track sound records, thecombination of two photoelectric tubes, one for each sound track andadapted to be energized by a beam of light scanning the half-waves insaid sound track, one of said photoelectric tubes being provided with ananode adapted to emit substantially twice as many secondary electrons asthe number of primary electrons striking the same, said primaryelectrons being produced in response to the beam of light scanning thesound track, an auxiliary anode associated with said anode forattracting said secondary electrons and effective to invert the phase ofthe half-waves of the respective sound track, whereby the two half-wavesof the sound record reproduced thereby are arranged in phase opposition.

5. In a system for reproducing balanced double track sound records, aphotoelectric tube comprising within an envelope, two separate anodesand a common cathode, a shield on said cathode and dividing the same intwo portions, each of which being positioned opposite one ofsaid anodes,said shield preventing the electrons produced on one portion of saidcathode in response to a light beam scanning the half-waves in one ofsaid sound tracks from passing'to the other cathode portion whichisadapted to be struck by a light beam scanning the half-waves in theother sound track, one of said anodes being adapted to emit multipliedsecondary electrons when struck by the primary electrons coming from therespective cathode portion, and an auxiliary screen anode surroundingsaid last named anode and being effective to invert the phase of thehalf-waves of the respective sound track, whereby the two half-waves ofthe sound record reproduced thereby are arranged in phase opposition.

6. In a system for-reproducing balanced double track sound records, thecombination of two photoelectric means, one for each sound track andadapted to be energized by a beam of light scanning the half-waves inthe sound track, one of said photoelectric means being provided withmeans for causing the electrons produced by the light scanning the soundtrack to produce multiplied secondary electrons so that the resultingelectron current in said photoelectric means flows in a directionopposite to the flow of the electrons produced in the otherphotoelectric means, whereby the reproduced two half-waves of the soundrecord are in phase opposition, and adjustable light absorbing meanspositioned in the path of at least one of the two separate light beamsscanning said two sound tracks for balancing the sensitiveness of saidtwo photoelectric means.

7. In a system for reproducing balanced double track sound records, aphotoelectric tube comprising within an envelope, two separate anodesand a common cathode, a shield on said cathode and dividing the same intwo portions, each 01' which being positioned opposite one of saidanodes, said shield preventing the electrons produced on one portion ofsaid cathode in response to a light beam scanning the half-waves in oneof said sound tracks from passing to the other cathode portion which isadapted to be struck by a light beam scanning the half-waves in theother sound track, one of said anodes being adapted to emit multipliedsecondary electrons when struck by the primary electrons coming from therespective cathode portion, an auxiliary screen anode surrounding saidlast named anode and being effective to invert the phase of thehalf-waves of the respective sound track, whereby the two half-waves ofthe sound record reproduced thereby are arranged in phase opposition,and means for applying a separate variable potential to at least one ofsaid anodes for balancing the electron production.

GERHARD CLAMANN.

